1. Field of the Invention
This invention relates to a gas-fired rotary industrial process furnace, adapted for the treatment by drying and/or calcining of materials and collection of the treated materials.
2. Prior Art
A variety of industrial process furnaces are known and have been designed with features that provide for the various considerations found in the drying and/or calcining of materials. Such considerations include, for example, the temperature required; whether the furnace should be of the direct-heat type requiring direct contact between the hot gases and the material being treated, or the indirect-heat type wherein heat is transferred by conduction through a wall to the material being treated; whether the operation should be continuous or batch; the particular materials to be treated, the economy of the construction and the operation of the furnace, etc.
U.S. Pat. No. 3,228,454 discloses a drum dryer of the indirect-heat type wherein the inside of a rotating drum is heated with steam while a slurry of the product to be heated is applied to the outside of the drum. As the drum rotates, the product is dried and then removed by means of a doctor blade. The apparatus is used for relatively low temperature operations such as the drying of cereals.
U.S. Pat. No. 5,299,512 discloses a burner designed for a rotary kiln and utilizing a particulate solid fuel, such as coal dust, with a liquid or gaseous fuel. The apparatus comprises concentrically positioned pipes to provide annular channels for the introduction of air, coal dust, and a liquid or gaseous fuel.
U.S. Pat. No. 5,123,361 discloses an annular vortex combustor having an outer vertical exhaust chamber. Fuel, such as powdered coal or coal water fuel, and air are injected tangentially near the bottom of the combustion chamber. Additional air is injected at selected points along the length of the combustion chamber.
U.S. Pat. No. 4,144,019 discloses a burner of the double vortex type wherein combustion gases and particulate travel in a spiral path through an outer cylindrical combustion chamber, then reverse direction to flow through an inner cylindrical combustion chamber and exit therefrom.
U.S. Pat. No. 3,799,252 discloses a roller drier wherein material to be dried is fed to the roller by means of a cylindrical feeding device and the dried material removed by means of a doctor blade.